1. Field of the Invention
The present invention relates to display art for a display device with three primary color R, G, and B light emitting elements aligned, more specifically, the present invention relates to a color display at sub-pixel accuracy (the term color display in the present specification includes grayscale display and general color display).
2. Description of the Related Art
Conventionally, display apparatuses using various display devices have been used. Among such displays, for example, color LCDs, color plasma displays, and organic EL (electroluminescent) display apparatuses have a display screen in which three light emitting elements for emitting three primary colors R, G, and B are aligned in a fixed order to form one pixel. A plurality of pixels are aligned in a first direction to form one line. A plurality of thus formed lines are aligned in a second direction orthogonal to the first direction to form a display screen.
For example, display devices in cellular telephones and mobile computers, include many display devices which have a relatively narrow display screen and in which it is difficult to see detailed expressions. If an attempt is made to display small characters, photographs, and complicated figures with such a display device, part of the image easily loses its details and becomes unclear.
In order to improve display clarity on a narrow screen, on the Internet, literature (titled “Sub Pixel Font Rendering Technology”) relating to sub-pixel display using a construction in which one pixel is formed of three R, G, and B light emitting elements is disclosed. The present inventors checked this literature upon downloading from a website provided by the Gibson Research Corporation (GRC) on Jun. 19, 2000. The principal disclosure from this web site is being filed with this application.
Referring now to FIG. 5 through FIGS. 9, the image of the alphabetic letter “A” is taken as an example of the image to be displayed.
FIG. 5 schematically shows one line where each pixel is formed of three light emitting elements. The horizontal direction in FIG. 5 (alignment direction of the three primary color R, G, and B light emitting elements) is referred to as a first direction. The vertical direction orthogonal to the first direction is referred to as a second direction.
Other alignment patterns can also be considered for the alignment of the light emitting elements in addition to the order of R, G, and B. Even when the alignment pattern is changed, this prior art and the present invention can be applied in the same manner.
The pixels thus formed of three light emitting elements are aligned in the first direction to form one line. The lines thus formed are aligned in the second direction to form a display screen.
Referring now to FIG. 6, original image data is acquired. Then, as shown in FIG. 7, three-time magnified image data is obtained by enlarging the original image data in the first direction (at a magnification equal to the number of R, G, and B light emitting elements).
Referring now to FIG. 8, colors are determined as shown for each pixel of FIG. 6. However, if display is made in this condition, color irregularities occur. Therefore, filtering is applied using luminance coefficients as shown in FIG. 9(a). A central target pixel is multiplied by a coefficient of 3/9, the next pixel is multiplied by a coefficient of 2/9, and the pixel after the next is multiplied by a coefficient of 1/9. whereby the luminance of each pixel is adjusted.
When filtering is applied to color pixels shown in FIG. 8, the pixels are adjusted as shown in FIG. 9(b). In the adjustment, blue is adjusted to light blue, yellow is adjusted to light yellow, reddish-brown is adjusted to light brown, and navy blue is adjusted to light navy blue.
An image that has been thus subjected to filtering is displayed by means of sub-pixel display by allocating the image to each light emitting element of FIG. 7.
However, in this display method, basically, only monochrome binary sub-pixel display is possible, and color image sub-pixel display is not possible.